M42 feb 2010

M42 taken from the Burren on Fri 12th Feb.
4 Shots stacked in Registax and level adjusted in PS.
Maybe slightly too purple / green?

Clouds came in so I couldnt get many shots...
Next time...
I'm aiming for 10 shots and darks / flats.

Hi Frank,

Great shot, colour looks good to me. Nicely framed and your tracking looks good too.

Question. Why are you aiming for 10, why not make it like 30 subs and get an absolutely killer image? Looks like the gear is well up to it.

Thanks Dave.
10 coz I don't really know how many I shoud take.
:laugh:
I reckoned if I started at say 10 sec and then did
20, 30, 40, 50 , 60 etc that it would be enough.
(honestly - I havent a clue!)
Just guessing it.

I know I need to take darks and flats
and then put all the shots into DSS.

The Astrotrac is a savage bit of kit and
if properly aligned (and no wind!) then the
shots are bang on.

It's still only a 70 mm Skylux...
I've got a focal reducer on the way for the ETX
so its more sturdy a set up and the optics are better
but slower.

Any other tips I'm all ears!

I was thinking I'd go for the Pliedies next..
size would be good.

How about using a short focal lenght refractor of say 400mm. That would give you a wider field of view and allow longer exposures.Short tube refractors are pretty cheap.

Frank

As the integration time goes up (indivdual exposure times number of exposures) so does the signal to noise ratio - but only by the square root of whatever the increased factor is. When SNR goes up this can be read as "graininess goes down".

Another way of looking at it is to say every time you increase the integration time by a factor of four you double the signal to noise ratio (cut the "graininess" by half).

Your image looks sweet and milky as posted. If you look at the original image closely yourself you may well spot that not all the milkyness is as milky as you'd like (ie signs of "grain") and if so you know that you can half that with four times the integration time or reduce it to one quarter of what it is by going for 16 times your current interagtion time.
That's the basic metrics of it.

But you basically go for as long as you can when dealing with faint stuff.

I speak more from the theoretical and from gleaming from others - I am not a seasoned practictioner.

Mark

Bang on what the lads have said there Frank, the more shots the better, it IS worth the effort, try to take as many darks as you can too, I would usually do this when packing uo for the night by taking the camera off, and letting it run with the cap on while putting away the gear - beats standing there in the cold

I am seriously planning on getting an astrotrac too, if it is a sgood as it can perform, try even 30 second exposures upwards, pushing it as hard as you can. The 70mm is fine for the brighter objects, you'd be surprised at what all these little things can add up to.

Keep it up!

Keith.